Osisko Mining Files Early Warning Report in Respect of Barkerville Gold Mines Limited

TORONTO, Sept. 28, 2017 - Osisko Mining Inc. (TSX:OSK) (the "Corporation") announces that it has filed an early warning report in respect of its holdings in Barkerville Gold Mines Ltd. ("Barkerville"). Earlier today, the Corporation, through its wholly-owned subsidiary O3 Investments Inc., acquired beneficial ownership of, or control and direction over, 7,500,000 common shares of Barkerville (collectively, the "Purchased Securities"), comprised of (i) 1,944,000 common shares of Barkerville by way of a brokered private placement (the "Private Placement"), and (ii) 5,556,000 common shares of Barkerville by way of a private agreement (the "Private Agreement"). The Corporation paid aggregate consideration of $6,000,000 for the Purchased Securities, representing a purchase price of $0.80 per share.

Immediately prior to the acquisition of the Purchased Securities, the Corporation, through its wholly-owned subsidiary O3 Investments Inc., had beneficial ownership of, or control and direction over, (i) 62,025,270 common shares of Barkerville, representing approximately 16.0% of the number of shares then issued and outstanding on a basic basis (being 388,815,997 shares), and (ii) 2,662,454 common share purchase warrants of Barkerville, representing together with the 62,025,270 common shares of Barkerville, approximately 16.5% of the number of shares then issued and outstanding on a partially-diluted basis (assuming only the exercise of the 2,662,454 common share purchase warrants of Barkerville held by the Corporation).

Immediately following the acquisition of the Purchased Securities, the Corporation, through its wholly-owned subsidiary O3 Investments Inc., had beneficial ownership of, or control and direction over, (i) 69,525,270 common shares of Barkerville, representing approximately 16.5% of the number of shares issued and outstanding on a basic basis (being 422,565,997 shares), and (ii) 2,662,454 common share purchase warrants of Barkerville, representing together with the 69,525,270 common shares of Barkerville, approximately 17.0% of the number of shares issued and outstanding on a partially-diluted basis (assuming only the exercise of the 2,662,454 common share purchase warrants of Barkerville held by the Corporation).

The Corporation, through its wholly-owned subsidiary O3 Investments Inc., acquired the Purchased Securities for investment purposes, and to maintain its approximate pro-rata equity interest in Barkerville. The Corporation has no current intention of increasing or decreasing its ownership of, or control or direction over, additional securities of Barkerville. The Corporation reviews its holdings from time to time and may increase or decrease its position as future circumstances may dictate.

This news release is being issued in accordance with National Instrument 62-103 – The Early Warning System and Related Take-Over Bid and Insider Reporting Issues in connection with the filing of an early warning report dated September 28, 2017. The early warning report respecting this transaction has been filed on System for Electronic Document Analysis and Review ("SEDAR") at www.sedar.com under Barkerville's issuer profile. To obtain a copy of the early warning report filed by the Corporation, please contact John Burzynski at (416) 363-8653 or refer to SEDAR at www.sedar.com under Barkerville's issuer profile.



For further information on the Corporation please contact:

John Burzynski, President & Chief Executive Officer
Telephone: (416) 363-8653

The Corporation's head office is located at 155 University Avenue, Suite 1440, Toronto, Ontario M5H 3B7.